The Naval Service has been ordered to remove mines from a German U-boat on the Cork coast amid fears that unauthorised divers may trigger an explosion on the submarine, which is lying close to an underwater gas line.

The Naval Service has inspected the wreck of the UC42 on a number of occasions and recently discovered that seals it had put on the submarine had been tampered with. Unauthorised divers are suspected of having gained access to the site.

The UC42, which sank at the entrance to Cork harbour on September 10, 1917, is laden with mines. It was laying mines from special underwater tubes when an explosion occurred in its stern, resulting in the loss of all 27 crew onboard.

The submarine was discovered by a group of amateur divers off Roche’s Point nearly five years ago and is still relatively well preserved. It is also classified as a war grave.

The order to remove the mines was issued to the Naval service yesterday by the Department of Arts, Heritage, and the Gaeltacht, which is the agency responsible for wrecks.

David Stanton, chairman of the Oireachtas Committee on Justice and Defence, said the order was issued because it was important the make the area safe.

“I would urge people to keep away from the submarine because of two issues — it is a war grave and people should respect that, and there is obviously a possibility that they could inadvertently trigger the mines,” said Mr Stanton.

It is unclear when navy divers would start the operation, but Mr Stanton said before it could commence “an ecological risk assessment would be carried out as a priority” to see if there was any threat to marine wildlife.

The Naval Service has, over the years, made safe a number of mines which drifted onto beaches or got tangled in trawler nets. These were mainly Second World War mines.

However, this will be the first time that navy divers will remove ageing and potentially unstable mines from a submarine.